Calcium signaling plays a key role in many cellular processes including proliferation and differentiation of hematopoietic cells, muscle contraction, actin filament disassembly and long term potentiation. One essential component of intracellular calcium dynamics is release of intracellular calcium stores via inositol 1,4,5-trisphosphate receptors (IP3Rs). In the nematode Caenorhabditis elegans (C. elegans), the IP3R regulates a behavioral rhythm - the periodic contraction of the posterior body wall muscles. The intestine controls the contraction of the overlying muscles in a nonautonomous fashion and intestinal calcium oscillations directly precede the muscle contraction. How the activity of the IP3R within one tissue, the intestine, modulates the activity of another tissue, the muscle, is unknown. This proposal aims to uncover the molecular and cellular basis of the fast, novel signaling cascade initiated by IP3R function in the nematode Caenorhabditis elegans. The following Aims will be addressed. Specific Aim 1: Sufficiency and necessity of calcium spike in induction of the posterior body contraction Specific Aim 2: Determination of the spatial and temporal characteristics of calcium dynamics in the intestine Specific Aim 3: Determination of the molecular basis of the signal that directs posterior body contraction . .